Network Working Group Gargi Nalawade
Internet Draft Ruchi Kapoor
Expires: December 2003 Dan Tappan
Cisco Systems
IPv4-Tunnel SAFI
draft-nalawade-kapoor-tunnel-safi-00.txt
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
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Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
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The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
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2. Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
3. Abstract
There is a need for Tunnel end-point discovery within and across
Autonomous Systems. BGP is the only protocol that is widely-spoken
across Autonomous Systems and can carry this information. This
document defines how BGP speakers can convey Tunnel end-point
reachability information.
4. Introduction
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Internet Draft draft-nalawade-kapoor-tunnel-safi-00.txt June 2003
Two end-points of a Tunnel need to know the end-point information and
its binding to a network address at the remote point. Normally, this
can be statically shared and configured. But in case of a large
network where there may be a need for a large number of tunnels, the
number of tunnel end-points that need to be exchanged and maintained,
grows. It then needs to be exchanged and maintained using an inter-AS
protocol.
5. The IPv4-Tunnel SAFI
This document defines a new SAFI called the IPv4-Tunnel SAFI. The
<AFI, SAFI> [IANA-AFI] [IANA-SAFI] value pair used to identify this
SAFI is (AFI=1, SAFI=TBD).
The tunnel end point address will be carried as an NLRI in the
MP_REACH attribute for this SAFI. The NLRI Format will be a 2-byte
Reserved field followed by a 4-byte IPv4 address.
6. BGP Attribute
The BGP SSA Attribute [BGP-SSA] will be used to carry the Tunnel
end-point information.
The Value Field of the BGP SSA Attribute, MUST contain at least one
of the following valid Type codes for this SAFI. It MAY contain one
or more TLVs with these Type codes.
Type 1: L2TPv3 Tunnel information
Type 2: mGRE Tunnel information
Type 3: IPSec Tunnel information
Type 4: MPLS Tunnel information
6.1. L2TPv3 Tunnel information TLV
The L2TPv3 Tunnel Information TLV has a type of 1. The value part of
the L2TPv3 Tunnel Information Type contains the following :
- Preference (2 Octets)
- Flags (1 Octet)
- Cookie Length (1 Octet)
- Session ID (4 Octets)
- Cookie (Variable)
The L2TPv3 Tunnel Information TLV looks as follows :
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0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x01 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Preference (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Flags | Cookie Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session ID (4 Octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Cookie (Variable) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where
Length A 2 Octet field that specifies the length of the L2TPv3
attribute in octets. The value contained in this Length field MUST
not exceed the total length of the BGP SSA [SSA] Attribute minus the
total length of any prior TLVs.
Preference A 2 Octet field containing a Preference associated with
the TLV. The Preference value indicates a preferred ordering of
tunneling encapsulations according to the sender. The recipient of
the information SHOULD take the sender's preference into account in
selecting which encapsulation it will use. A higher value indicates a
higher preference.
Flags A 1 Octet field containing flag-bits. The leftmost bit
indicates whether Sequence numbering is to be used or not. The
remaining bits are reserved for future use.
Cookie Length Cookie Length is a 1 Octet field that contains the
length of the Variable length Cookie.
Session ID A 4 Octet field containing a non-zero identifier for a
session.
Cookie Cookie is a variable length (maximum 64 bits), value used by
L2TPv3 to check the association of a received data message with the
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session identified by the Session ID.
The default value of the Length Field for the L2TPv3 Tunnel
information TLV is between 8 and 16 bytes, depending on the length of
the Cookie field specified in Cookie length. If the length of the TLV
is greater than that value, the subsequent portion of the Value field
contains one or more sub-TLVs.
A Sub-TLV when present is of the following format :
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value (Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where Sub-Type & Length are of 1-Octet each & the Value field is
variable as specified by the Length.
6.2. mGRE Tunnel Information TLV
The mGRE Tunnel Information Type has a Type 2. The value part of the
mGRE Tunnel Information Type contains the following :
- Preference (2 Octets)
- Flags (1 Octet)
- mGRE Key (0 or 4 Octets)
The mGRE Tunnel Information TLV looks as follows :
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x02 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Preference (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|K| Flags | |
+-+-+-+-+-+-+-+-+ |
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| mGRE Key (4 Octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Length A 2 Octet field that specifies the length of the mGRE
information in octets. The value contained in this Length field MUST
not exceed the total length of the BGP SSA [SSA] Attribute minus the
total length of any prior TLVs.
Preference A 2 Octet field containing a Preference associated with
the TLV. The Preference value indicates a preferred ordering of
tunneling encapsulations according to the sender. The recipient of
the information SHOULD take the sender's preference into account in
selecting which encapsulation it will use. A higher value indicates a
higher preference.
Flags A 1 Octet field containing flag-bits. The leftmost bit
indicates whether Sequence numbering is to be used or not. The 2nd
bit indicates whether an mGRE Key is present or not. The remaining
bits are reserved for future use.
mGRE Key A 4 Octet field containing an optional mGRE Key.
If the Length field of the TLV contains a value greater than 3 Octets
plus the value specified in the Key Length, the subsequent portion of
the Value field contains one or more sub-TLVs.
A Sub-TLV when present is of the following format :
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value (Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where Sub-Type & Length are of 1-Octet each & the Value field is
variable as specified by the Length.
6.3. IPSec Tunnel Information TLV
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The IPSec Tunnel Information Type has a Type 3. The format of the
IPSec Tunnel Information TLV is TBD.
6.4. MPLS TLV
The MPLS TLV has a Type 4. The format of the MPLS TLV is TBD.
7. Capability Advertisement
A BGP speaker that wishes to exchange the IPv4-Tunnel SAFI, MUST use
the MP_EXT Capability Code as defined in [BGP-MP], to advertise the
corresponding (AFI, SAFI) pair.
A BGP speaker MAY participate in the distribution of IPv4-Tunnel
information.
8. Operation
A BGP Speaker that receives the Capability for the IPv4-Tunnel SAFI,
MAY advertise the IPv4-Tunnel prefixes to that peer.
In the UPDATE message for this SAFI sent to a peer, a BGP speaker
MUST only advertise the SAFI-specific attribute [SSA] TLVs that are
defined as valid for this SAFI.
If a BGP Speaker receives an SSA TLV that it does not recognize, it
will accept it and propagate it to other peers.
9. Deployment Considerations
In order for the Tunnels to come up between two end-points, the BGP
Speakers advertising the Tunnel end-points using the Ipv4 Tunnel
SAFI, MUST exchange at least one common encapsulation option.
10. Security Considerations
This extension to BGP does not change the underlying security issues.
11. Acknowledgements
We would like to thank Jim Guichard, Arjun Sreekantiah, Shyam Suri,
Chandrashekhar Appanna, John Scudder and Mark Townsley for their
comments and suggestions.
12. References
[IANA-AFI] http://www.iana.org/assignments/address-family-numbers
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[IANA-SAFI] http://www.iana.org/assignments/safi-namespace
[BGP-4] Rekhter, Y. and T. Li (editors), "A Border Gateway Protocol
4 (BGP-4)", Internet Draft draft-ietf-idr-bgp4-17.txt, January 2002.
[BGP-CAP] Chandra, R., Scudder, J., "Capabilities Advertisement with
BGP-4", draft-ietf-idr-rfc2842bis-02.txt, April 2002.
[BGP-SSA] Kapoor R., Nalawade G., "BGPv4 SAFI-Specific Attribute",
draft-nalawade-kapoor-bgp-ssa-00.txt, work in progress.
[MULTI-BGP] Bates et al, Multiprotocol Extensions for BGP-4, draft-
ietf-idr-rfc2858bis-02.txt, work in progress.
[IPSEC-ARCH] Kent, S., and R. Atkinson, "Security Architecture for
the Internet Protocol", RFC 2401, November 1998.
13. Author's Addresses
Gargi Nalawade
Cisco Systems, Inc
170 West Tasman Drive
San Jose, CA 95134
mailto:gargi@cisco.com
Ruchi Kapoor
Cisco Systems, Inc
170 West Tasman Drive
San Jose, CA 95134
mailto:ruchi@cisco.com
Dan Tappan
Cisco Systems, Inc
170 West Tasman Drive
San Jose, CA 95134
mailto:tappan@cisco.com
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16. Expiration Date
This memo is filed as <draft-nalawade-kapoor-tunnel-safi-00.txt>, and
expires December, 2003.
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